Prior to the present invention, processing difficulties were encountered when dispersing and incorporating dry polysaccharides, such as methylhydroxypropylcellulose (MHPC) and hydroxypropylcellulose (HPC), into water-containing liquid formulations using conventional methods of dispersion. It is well known that cellulosic polymers are widely used as thickening agents in aqueous based liquid formulations, such as liquid detergents, conditioners, shampoos, liquid hand soaps, and the like. Known prior art methods to overcome difficulties during dispersion of the dry MHPC into the formulation include: dispersion by heating the water to temperatures of 60-100.degree. C.; dispersion by slurrying the cellulose ether in water miscible organic liquids such as alcohol or glycol; and dispersion by dry blending the cellulosic with powders. The disadvantages of these methods are the use of large amounts of energy in the form of heat, and long mixing cycles, and the presence of inflammable solvents, such as alcohol, which create the danger of a fire.
Still another difficulty encountered in the aforesaid dispersion methods is the formation of lumps of undissolved polysaccharide polymer in the aqueous medium which do not dissolve even after protracted periods of agitation (about 2-3 hours). This lumping problem requires an additional filtration step to rid the liquid formulation of said undissolved material. There is also a loss of thickening power when such undissolved material is filtered from the solution, which often requires re-work of the formulation.
Many prior art references exist that try to alleviate the above mentioned problems in the use of dry polysaccharide by using heated water and/or oil phases in order to disperse and dissolve the polymer prior to the addition to a formulation, such as for skin conditioning, detergents, shampoos, and the like. See U.S. Pat. Nos. 3,953,591, 3,549,542, 3,998,761, and 4,174,305.
Another approach for solving the above mentioned problems for incorporating polysaccharide polymers into household liquid formulations containing water is the use of a pre-mix of polymers dispersed in a water free liquified organic medium in which it does not swell or dissolve, prior to its incorporation into an aqueous formulation, using a short mixing cycle. This approach was described in U.S. Pat. No. 4,469,627.
None of the above prior art references discloses the incorporation into household and personal care products of a fluid polymer suspension system of polysaccharides. U.S. Pat. No. 4,883,536 discloses fluid polymer suspensions of cellulosic polymers using ammonium salts having multivalent anions that could be used in personal care products. An anonymous publication in a research disclosure in Derwent Week 1980-30 having a nominal publication date of Jul. 10, 1980 (publication DR 195006) is directed to a probable slurry of a cellulose ether comprising a methylcellulose derivative in an aqueous liquid with a sufficient amount of a water soluble salt of sodium carbonate or potassium carbonate to insolubilize the ether in the aqueous liquid. This anonymous publication does not suggest any potential use for this particular composition, nor does it give information enabling one to utilize these slurries in the present composition.